The present invention relates generally to a sorting system and more particularly to a system using an electromagnetic radiation source to separate one item from a plurality of items.
It will be appreciate by those skilled in the art that items such as plastic and paper need to be recycled. Unfortunately, when it is received at a recycling station, this material is often commingled so that plastic and paper are commingled as well. Additionally, plastics of various types are also commingled. To this end, there have been several attempts to sort these materials. One such attempt is described in the Meas. Sci. Technology in 1995 which discloses a 2-color near-infrared sensor for sorting recycled plastic waste. This particular descriptions uses a split near infrared region of the electromagnetic spectrum to sort different types of polymers. This particular item explains how PET and PVC can be distinguished. Unfortunately, this disclosure uses a beam splitter which is very ineffective and can be difficult to use in the field because it must be fabricated to a suitable tolerance. Also, the angle must be maintained carefully to assure a good split. Additionally, the splitter required in the disclosure must be electroplated with gold. As a result, it can be very expensive. The hardware implementation specified in this paper uses a logarithmic amplifier in an attempt to measure the actual absorbence of a material. In reality, this technique is not practical because it assumes that the material being measured is perfectly clean and has a negligible reflectance. This is clearly not the case for a post-consumer recycling application.
What is needed, then, is a system and method for distinguishing items from a plurality of items. This needed system must be easy to use in the field and efficient to manufacture. This needed system must be capable of reading multiple wavelengths. This system is presently lacking in the prior art.